1. Field of the Invention
The present invention relates to means for eliminating leakage current in electrical signals traveling through circuits, and particularly to a circuit for eliminating leakage current in a signal by use of a field-effect transistor.
2. Description of the Prior Art
Electric leakage is an endemic problem for designers of digital circuits. FIG. 1 is a schematic diagram of transmission of signals accompanied by electrical leakage. Leakage current exists in a first electronic system 1. The leakage current is transmitted with the signals to a second electronic system 2 via transmission lines. The leakage current causes noises in the signals. Furthermore, the leakage current may generate an electromagnetic field, and the generated electromagnetic field may interfere with proper operation of the second system 2.
In order to eliminate leakage current, one solution is to employ so-called designer integrated circuits (ICs). However, the cost of designer ICs is generally considerably high. Another solution is to use a common IC, such as a 7404-type IC, to isolate the leakage current from the signals. Nevertheless, in most cases, only very few signal lines need to be isolated. If an IC is employed to achieve isolation, the cost of the IC is still disproportionately high compared to the benefit derived by the handful of signal lines. Therefore, a simple and economical solution is needed for solving the problem of the leakage current in these circumstances.